What is Relay? All Types, Applications, Working Principle?

Relays can be considered as one of the key elements in the branch of electrical and electronic circuits that allow controlling powerful circuits with the help of low-strength signals. To mention an example of the simplicity of the relay, we may speak about an ordinary home appliance, and to mention an example of the complex relay system, we may speak about an industrial automation system. So, what is relay, and how does it work? This blog will discuss what relays are, the kinds of relays, and the diverse uses of relays will be discussed.

What is Relay?

An electrical example of a relay can be defined by coming up with the understanding that a relay is an electric switch. An overload relay is a device which has an electromagnetic coil which, when supplied current, opens or closes some or all the contacts to make or break the current in a circuit. In other words, relays enable one circuit to deal with another, and this normally involves varying currents and voltage. This makes relays very essential in low-power electronic circuits and even in high-power electrical circuits.

The main job of a relay is to switch a circuit on the basis of a different low-power signal or several signals. For example, a small current from a control circuit can energise the relay which then closes a circuit for a larger high power current. This separation of the control circuit and the controlled circuit is a good safety precaution since the control circuit that is handling the low voltage signals cannot be affected by high voltage signals or spikes.

How Does Relay Work?

A relay literary works based on the force created by current through a coil and named electromagnetic force. When the coil is energised, a magnetic field is developed, and this causes a lever or armature to be attracted, thus operating the contact points and opening or making them close. When the current is switched off. However, a spring lets the core back to its original position, either pulling the contacts back up or down. Here’s a step-by-step explanation of the relay module working principle:

• Energising the Coil: When an electrical current is passed through the coil of the relay, it causes a magnetic field. The strength of this field is proportional to the amount of the current passing through the coil.
• Magnetic Attraction: The magnetic field pulls on a switch-like component called the Armature, which is in a position of interaction with the contacts it makes.
• Switching the Contacts: In its movement, the armature either makes or breaks the circuits in the relay’s contacts. This switching action either makes or opens a circuit and, in this way, regulates the flow of current.
• De-energising the Coil: When the current is switched off, the magnetic field dies back, and the armature moves back to its original position due to the attraction of the spring that has been used in the circuit in a reversal of the contacts.

This single yet useful relay module working principle forms the basis of operations for the relays in so many applications.

Types of Relay

As is the case with almost every other electrical component, there is a wide range of relays, all of which are optimised to offer certain performances depending on the intended use. In order to review the types of relay and recommend suitable ones in certain application areas, it is important to gain knowledge about them. Here are some of the most common types:

Electromagnetic Relays

These are the most elementary ones and are extensively used in electrical applications. Electromagnetic relays work on the basis of electromagnetism, wherein the magnetic field created by the coil closes the circuit of the switch. They are widely incorporated into automotive applications, industry control systems and home use.

Solid-State Relays (SSRs)

In solid-state relays the switching action is done without the use of mechanical parts as used in the normal relays, but parts made of semiconductors are used instead. They are faster in signal transmission, highly dependable and longer in the span of their life cycle, unlike the electromagnetic relays that contain certain mechanical switching components. Due to the capability to switch quickly and sustain a considerable number of cycles, SSRs are excellent for use in automation and machinery.

Reed Relays

Reed relays are electromagnetic types of relay having the contact points shielded in a glass bulb. The contacts are of ferromagnetic material, and the same are kept enclosed in the tube, which is evacuated and filled with an inert gas.

Thermal Relays

Thermal relays are used with the help of the thermal effect in metals, leading to thermal expansion. They are employed in the protection circuits of motors and other electrical appliances against overload. The extra current over a certain limit trips the relay through an effect of heat; this bends the bimetallic strip in the relay, opening the circuit above the equipment.

Time-Delay Relays

Time-delay relays are definitely used to delay the onset of contact opening or contact closing. These relays are commonly used where timing control is of paramount importance like the lighting systems, the motor control circuits, and the automation processes.

Hybrid Relays

Such relays are formed when electromagnetic and solid-state are combined, which makes Hybrid relays have useful features of both types of relays. These are employed in systems which are critical and accurate in operation; for example, in aviation and military industry.

Application of Relay

Relays are extensively used in devices and apparatus throughout the residential and commercial sectors to the industrial level. Due to their flexibility in use, relays are applied in practically all electrical and electronic circuits. Here are some of the key application of relay:

Automotive Industry

In the automotive industry, relays are used to control many operations, for example, headlights, horns, wiper control, and the starter motor. They enable low-signal power from switches and sensors to regulate high-signal power circuits of the vehicle, making them safe and efficient to use.

Home Appliances

Relays are extensively incorporated in home appliances for use in regulating the functioning of motors, heaters or compressor devices. For instance, in a refrigerator, the relay manages the compressor motor where the current will be switched on and off depending on the desired temperature.

Industrial Automation

In industrial automation, control relays are also applied for the regulation of the equipment, conveyors, and other production lines. They afford the needed separation of control circuits from high-power machinery so as to enhance safety and efficiency.

Telecommunications

Reed relays are commonly applied in telephone exchanges and other related communication systems because of their high speed of switching and high efficiency.

Power Systems

In power systems relays are employed in protection and control applications. It is used for the protection of electrical equipment from faults, including overload and short circuits. Simplified protection relays monitor the abnormalities established within the power system, and they promptly isolate the defective segment by throwing the circuit breakers in an effort to avoid further destruction and to maintain the stability of the system.

Railway Signalling

Relays are widely used in railway signalling schemes to control signals, track circuits and interlocking systems. They control the flow of electricity to several signalling apparatuses to facilitate the proper and safe running of trains.

Functions of Relay

The functions of relay do not limit its operation to only switching. Relays are essential elements that can manage multiple critical operations in electrical and electronic circuits. Here are some of the key functions of relay:

Circuit Isolation

The major roles of the relay include offering a path to the control circuit as well as offering electrical isolation between the control circuit and the controlled circuit. Isolation of the wires in this way protects delicate components from high voltage and current in the controlled circuit so that the lifespan of the system is not shortened.

Signal Amplification

Relays can be used to either boost signals or to enable a small control signal to power a larger load. This is very useful in instances where a small control signal is required to toggle a large load, for instance in a motor and or a light application.

Multiplexing

In a power control system, relays are beneficial in controlling several circuits as and when a particular control signal is needed. This multiplexing function is useful in those operations where more than one device or system has to be operated at one and the same time; this is common in automation and communication operations.

Overload Protection

In overload protection mechanisms, relays are employed to have the ability to sense and act upon high currents in that particular circuit. Thermal relays, for instance, guard motors and other related apparatus, from damage through the electric trip when the current gets high and is dangerous due to high heat.

Also Read: What is Control Relays: Types, Functions and Applications

Conclusion

For those looking to delve deeper into the world of relays, understanding the relay module working principle is a great starting point. This knowledge will enable you to design and implement reliable and efficient circuits that meet the demands of modern technology. Buy the best relays online easily from the eShop of Lauritz Knudsen Electrical and Automation.